perf: fast display (row runs, bulk fills, pixel scroll), terminal draws changed cells only + scrolls pixels, print! batched (was IPC per fmt fragment), snake sleeps on timer

crates/apps/snake/src/main.rs

@@ -47,8 +47,12 @@ fn main() {
         libkos::println!("snake: needs the display (see /bin/snake.manifest)");
         return;
     }
-    // Takes focus; the game polls every tick, so it never waits on the signal.
-    let _ = libkos::display::subscribe_input(display_ep());
+    let Ok(alarm) = syscall::create_notification() else {
+        libkos::println!("snake: no timer");
+        return;
+    };
+    // Takes focus; keys are polled every tick, the signal only wakes it.
+    let _ = libkos::display::subscribe(display_ep(), alarm, types::badge::Badge::new(1 << 1));
     let mut snake = Snake::new();
     let mut commands = [RenderCommand { x: 0, y: 0, w: 0, h: 0, color: 0 }; MAX_RENDER_CMDS];
 
@@ -67,12 +71,12 @@ fn main() {
             flush();
             // Any key leaves.
             while next_input() == Input::None {
-                wait_tick();
+                wait_tick(alarm);
             }
             return;
         }
 
-        wait_tick();
+        wait_tick(alarm);
         if handle_input(&mut snake) == Input::Quit {
             return;
         }
@@ -122,10 +126,17 @@ fn handle_input(snake: &mut Snake) -> Input {
     }
 }
 
-fn wait_tick() {
-    let start = syscall::get_time();
-    let deadline = Ticks::from_raw(start.raw() + TICK_DELAY);
-    while syscall::get_time().raw() < deadline.raw() {
-        syscall::yield_now();
+/// Sleeps until the next tick on `alarm`, instead of spinning. Keys
+/// signal it too (snake has one notification), so it waits again until
+/// the tick is really due.
+fn wait_tick(alarm: CapSlot) {
+    let deadline = syscall::get_time().raw() + TICK_DELAY;
+    if syscall::set_timer(alarm, Ticks::from_raw(deadline)).is_err() {
+        return;
+    }
+    while syscall::get_time().raw() < deadline {
+        if syscall::wait(alarm).is_err() {
+            return;
+        }
     }
 }